Preliminary work from our lab suggests that in humans the subventricular zone (SVZ) astrocytes function as neural stem cells and that the cytoarchitecture of the SVZ in humans is different from that of other mammals. We will perform experiments to determine the cytoarchitecture of the human SVZ and fates of its new cells by doing a serial reconstruction of the adult human SVZ with electron microscopy and by finding the exact location of adult human SVZ neural stem cells with immunocytochemistry techniques. This information is essential to raise hypothesis regarding the function of proliferative cells in the SVZ. We will learn if cells with the characteristics of transient amplifying cells, of young neurons or young oligodendrocytes, exist in the SVZ. Our second aim is to describe the SVZ-Olfactory Bulb (OB) system in adult human brain. We will study other possible pathways for adult human neuronal migration and we will characterize the adult human OB and tract. We will focus in the identification of young neuronal precursors using specific markers to explore possible migratory routes in the adult human brain and we will also investigate whether there is an intrinsic population of stem cells within the OB and how they may possibly migrate to supply other regions of the brain.